1. Field of the Invention
The present invention relates to exposure apparatus, exposure methods, and device manufacturing methods, and more particularly to an exposure apparatus and an exposure method used in a lithography process to manufacture microdevices such as a semiconductor device, and a device manufacturing method using the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper), or a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) is mainly used.
In this kind of exposure apparatus, the first thing required is to have a high throughput. As an approach for improving the throughput, various proposals are made also on a twin wafer stage type exposure apparatus which employs a method where a plurality of wafer stages holding a wafer, such as for example, two water stages, are arranged, and concurrent processing of different operations is performed on the two stages (refer to, for example, U.S. Pat. No. 6,262,796).
Furthermore, recently, a proposal has also been made on a twin water stage type exposure apparatus which employs a liquid immersion method (refer to, for example, U.S. Pat. No. 7,161,659).
However, in the case the exposure apparatus is equipped with two wafer stages as is described in, for example, U.S. Pat. No. 7,161,659, during the movement of each wafer stage between an exposure position (a position under the projection lens) and a position where wafer exchange (and wafer alignment) is performed, there was a position where measurement of an interferometer system measuring the position of the wafer stage becomes unmeasurable.